The present invention relates to film cooling, and more particularly to structures and methods for providing vortex film cooling flows along gas turbine engine components.
Gas turbine engines utilize hot fluid flows in order to generate thrust or other usable power. Modern gas turbine engines have increased working fluid temperatures in order to increase engine operating efficiency. However, such high temperature fluids pose a risk of damage to engine components, such as turbine blades and vanes. High melting point superalloys and specialized coatings (e.g., thermal barrier coatings) have been used to help avoid thermally induced damage to engine components, but operating temperatures in modern gas turbine engines can still exceed superalloy melting points and coatings can become damaged or otherwise fail over time.
Cooling fluids have also been used to protect engine components, often in conjunction with the use of high temperature alloys and specialized coatings. One method of using cooling fluids is called impingement cooling, which involves directing a relatively cool fluid (e.g., compressor bleed air) against a surface of a component exposed to high temperatures in order to absorb thermal energy into the cooling fluid that is then carried away from the component to cool it. Impingement cooling is typically implemented with internal cooling passages. However, impingement cooling alone may not be sufficient to maintain suitable component temperatures in operation. An alternative method of using cooling fluids is called film cooling, which involves providing a flow of relatively cool fluid from film cooling holes in order to create a thermally insulative barrier between a surface of a component and a relatively hot fluid flow. Problems with film cooling include flow separation or “liftoff”, where the film cooling flow lifts off the surface of the component desired to be cooled, undesirably allowing hot fluids to reach the surface of the component. Film cooling fluid liftoff can necessitate additional, more closely-spaced film cooling holes to achieve a given level of cooling. Cooling flows of any type can present efficiency loss for an engine. The more fluid that is redirected within an engine for cooling purposes, the less efficient the engine tends to be in producing thrust or another usable power output. Therefore, fewer and smaller cooling holes with less dense cooling hole patterns are desirable.
The present invention provides an alternative method and apparatus for film cooling gas turbine engine components.